"When you consider the cost to deliver the fuel to some of the most isolated places in the world — escorting, command and control, medevac support — when you throw all that infrastructure in, we're talking over $20 billion," Steven Anderson tells weekends on All Things Considered guest host Rachel Martin. He's a retired brigadier general who served as chief logistician for Gen. David Petraeus in Iraq. He's now in the private sector, selling technologies branded as energy-efficient to the Defense Department.

Now it's important to note that wrapped up in Anderson's $20 billion figure are all kind of other expenditures - for instance, the cost of building and maintaining roads in Afghanistan, securing those roads, managing the security operations for those roads. That all costs a lot of money and is part of the overall war effort in Afghanistan.

Anderson adds that the fuel to power the generators must pass over 800 miles of "improved goat trails" for two weeks after leaving depots in Pakistan.

The Pentagon rejects the estimate. If any Pentagon or military officials care to weigh in we'd love to hear from the other side.